The interface of poly(butylene terephthalate) (PBT) and sputtered titanium nitride (TiN) thin films was studied. The thin films were deposited by magnetron sputter ion plating (MSIP) onto the polymer. The interface analysis was performed after the deposition process, in which a layer of approximately 60 nm of titanium nitride was formed on the polymer. The influence of the plasma pretreatment parameters: (a) etch gas (Ar, O 2 , N 2 ) and (b) r.f. etching plasma bias power on the interface composition were studied with X-ray photoelectron spectroscopy (XPS) and argon sputter depth profiling. Results show that the adhesion of the coatings can be improved by sputter etching the polymer substrates prior to the deposition of the coating, but that the substrate itself also has a large influence on the chemical composition of the coating and the interface region.